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Abstract
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Manipulating the levels of antioxidative
defense system may affect leaf senescence and increase
yield. Phytohormones, reactive oxygen species, and
antioxidants interact in the regulation of plant metabolism.
Therefore, the aim of this study was to find out whether the
exogenous applications of BAP (a synthetic Cytokinin) and
ABA to wheat cultivars subjected to water stress could
influence the rate of H2O2, MDA (Malondialdehyde), and
enzymatic and non-enzymatic antioxidative defense systems.
For this purpose, a factorial experiment based on
randomized complete block design was carried out with
three replications. The experiment was performed on two
Iranian wheat cultivars (Pishtaz and Karaj3), under water
stress, using hormones. Plants were also exposed to water
stress after anthesis with daily pot weighing. BAP and
ABA were applied at the stage of initial grain filling,
starting 2 days post anthesis. Water stress resulted in
reduction of total Chl and AsA (Total Ascorbate) in both
cultivars. The reduction was lower in the tolerant cultivar
Pishtaz. In addition, water stress led to an enhancement in
MDA, H2O2, Car (Carotenoid), a-tocopherol, the activity
of CAT (Catalase), and POX (Peroxidase) and APX
(Ascorbate Peroxidase) enzymes. The tolerance of Pishtaz
cultivar under water stress is associated with low MDA and
H2O2 contents as well as high Chl (Chlorophyll), Car, atocopherol,
and AsA contents, which are closely related to
the activity of its enzymatic antioxidants (including CAT,
POX, and APX). BAP application alleviated oxidative
stress (H2O2 and MDA contents) in both cultivars. However,
the response was higher in the tolerant cultivar
Pishtaz than that in Karaj3. Our results showed that ABA
application resulted in an increase in the content of H2O2
and MDA, and the activities of CAT, POX, and APX
enzymes; moreover, it enhanced the contents of non-enzymatic
antioxidants such as AsA, Car, and a-tocopherol.
Consequently, it was found that hormones regulate leaf
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